In almost all computer applications, users must enter correct words for the desired objects or actions. For success without
extensive training, or in first-tries for new targets, the system must recognize terms that will be chosen spontaneously.
We studied spontaneous word choice for objects in five application-related domains, and found the variability to be surprisingly
large. In every case two people favored the same term with probability <0.20. Simulations show how this fundamental property
of language limits the success of various design methodologies for vocabulary-driven interaction. For example, the popular
approach in which access is via one designer's favorite single word will result in 80-90 percent failure rates in many common
situations. An optimal strategy, unlimited aliasing, is derived and shown to be capable of several-fold improvements.